Remote controller for controlling apparatus by diverting feedback signal from native controller to the remote controller and methods for same

ABSTRACT

A remote controller can be provided on any apparatus that employs feedback control from a native controller to add functionality to the apparatus where the native controller is not capable of providing such functionality independently.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a divisional of U.S. patent application Ser. No.15/378,874, filed Dec. 14, 2016, which claims benefit of the filing dateof U.S. Provisional Patent Application No. 62/267,003, filed Dec. 14,2015, both of which are hereby incorporated by reference.

TECHNICAL FIELD

The systems and methods described below generally relate to the field ofremote controllers for controlling a native feedback controller of anapparatus.

BACKGROUND

Injection molding is commonly used for manufacturing of parts made ofmeltable material, such as thermoplastic polymers. To facilitate theinjection molding of these parts, a solid plastic resin is introduced toa heated barrel that houses a reciprocating screw. The heated barrel andreciprocating screw cooperate to facilitate melting of the plastic andinjecting the melted plastic into a mold cavity for forming into adesired shape. Conventionally, an injection molding machine includes acontroller that controls various components during the molding process.

SUMMARY

In accordance with one embodiment, a method of manipulating a feedbacksignal for a native feedback controller of an apparatus is provided. Theapparatus further comprises a remote controller retrofit to the nativecontroller. The method comprises sensing a control variable of anactuation unit of the apparatus at a sensor and generating a feedbacksignal by the sensor based upon the control variable. At the remotecontroller the method further comprises receiving the feedback signal,generating a control signal based upon the feedback signal, combiningthe control signal and the feedback signal into a modified feedbacksignal, and transmitting the modified feedback signal to the nativecontroller in lieu of the feedback signal. The method further comprises,at the native controller, controlling operation of the actuation unit ofthe apparatus based at least in part upon the modified feedback signal.

In accordance with another embodiment, a method of controlling a controlvariable of an injection molding apparatus is provided. The injectionmolding apparatus comprises a heated barrel, an injection shaft, anactuation unit, and a native controller. The actuation unit is operablycoupled with the injection shaft and is configured to facilitateoperation of the injection shaft with respect to the heated barrel. Themethod comprises sensing a control variable of the injection shaft at asensor and generating a feedback signal by the sensor based upon thecontrol variable. At the remote controller, the method comprisesreceiving the feedback signal, comparing the control variable of theinjection shaft to a desired control variable setpoint, generating acontrol signal based upon the control variable and the desired controlvariable setpoint, combining the control signal and the feedback signalinto a modified feedback signal, and transmitting the modified feedbacksignal to the native controller in lieu of the feedback signal. At thenative controller the method further comprises controlling operation ofthe actuation unit based at least in part upon the modified feedbacksignal.

In accordance with another embodiment, an injection molding apparatuscomprises an injection molding apparatus that comprises a heated barrel,an injection shaft, an actuation unit, a clamping unit, a nozzle, anative controller, a remote controller, and a sensor. The injectionshaft is disposed in the heated barrel and is configured to rotate withrespect to the heated barrel. The actuation unit is operably coupledwith the injection shaft and is configured to facilitate operation ofthe injection shaft with respect to the heated barrel. The clamping unitis for a mold. The clamping unit is associated with the heated barrel.The nozzle is disposed at one end of the heated barrel and is configuredto distribute contents of the heated barrel to the clamping unit. Thenative controller is in communication with the actuation unit and isconfigured to facilitate operation of the injection shaft. The remotecontroller is in communication with the native controller. The sensor incommunication with the remote controller and configured to sense acontrol variable of the injection shaft. The remote controller isconfigured detect the control variable from the sensor and compare thecontrol variable to a desired control variable setpoint. The remotecontroller is further configured to generate a control signal based uponthe control variable and the desired control variable setpoint, combinethe control signal and the feedback signal into a modified feedbacksignal, and transmit the modified feedback signal to the nativecontroller in lieu of the first feedback signal. The native controlleris configured to control operation of the actuation unit based upon themodified feedback signal.

BRIEF DESCRIPTION OF THE DRAWINGS

It is believed that certain embodiments will be better understood fromthe following description taken in conjunction with the accompanyingdrawings in which:

FIG. 1 is a schematic view depicting an injection molding apparatus inaccordance with one embodiment; and

FIG. 2 is a block diagram depicting a native controller of the injectionmolding apparatus of FIG. 1 in association with a remote controller.

DETAILED DESCRIPTION

Embodiments disclosed herein generally relate to systems, machines,products, and methods of producing products by injection molding and,more specifically, to systems, machines, products, and methods ofproducing products by low, substantially constant pressure injectionmolding.

The term “substantially constant pressure” as used herein with respectto a melt pressure of a thermoplastic material, means that deviationsfrom a baseline melt pressure do not produce meaningful changes inphysical properties of the thermoplastic material. For example,“substantially constant pressure” includes, but is not limited to,pressure variations for which viscosity of the melted thermoplasticmaterial does not meaningfully change. The term “substantially constant”in this respect includes deviations of approximately 30% from a baselinemelt pressure. For example, the term “a substantially constant pressureof approximately 4600 psi” includes pressure fluctuations within therange of about 6000 psi (30% above 4600 psi) to about 3200 psi (30%below 4600 psi). A melt pressure is considered substantially constant aslong as the melt pressure fluctuates no more than 30% from the recitedpressure.

In connection with the views and examples of FIGS. 1-2, wherein likenumbers indicate the same or corresponding elements throughout theviews, FIG. 1 illustrates an injection molding apparatus 10 forproducing molded plastic parts. The injection molding apparatus 10 caninclude an injection molding unit 12 that includes a hopper 14, a heatedbarrel 16, a reciprocating screw 18, and a nozzle 20. The reciprocatingscrew 18 can be disposed in the heated barrel 16 and configured toreciprocate with respect to the heated barrel 16. An actuation unit 22can be operably coupled to the reciprocating screw 18 to facilitatepowered reciprocation of the reciprocating screw 18. In someembodiments, the actuation unit 22 can comprise a hydraulic motor. Insome embodiments, the actuation unit 22 can comprise an electric motor.In other embodiments, an actuation unit can additionally oralternatively comprise a valve, a flow controller, an amplifier, or anyof a variety of other suitable control devices for injection moldingapparatuses or non-injection molding apparatuses. Thermoplastic pellets24 can be placed into the hopper 14 and fed into the heated barrel 16.Once inside the heated barrel 16, the thermoplastic pellets 24 can beheated (e.g., to between about 130 degrees C. to about 410 degrees C.)and melted to form a molten thermoplastic material 26. The reciprocatingscrew 18 can reciprocate within the heated barrel 16 to drive the moltenthermoplastic material 26 into the nozzle 20.

The nozzle 20 can be associated with a mold 28 having first and secondmold portions 30, 32 that cooperate to form a mold cavity 34. A clampingunit 36 can support the mold 28 and can be configured to move the firstand second mold portions 30, 32 between a clamped position (not shown)and an unclamped position (FIG. 1). When the first and second moldportions 30, 32 are in the clamped position, molten thermoplasticmaterial 26 from the nozzle 20 can be provided to a gate 38 defined bythe first mold portion 30 and into the mold cavity 34. As the moldcavity 34 is filled, the molten thermoplastic material 26 can take theform of the mold cavity 34. Once the mold cavity 34 has beensufficiently filled, the reciprocating screw 18 can stop, and the moltenthermoplastic material 26 is permitted to cool within the mold 28. Oncethe molten thermoplastic material 26 has cooled and is solidified, or atleast partially solidified, the first and second mold portions 30, 32can be moved to their unclamped positions to allow the molded part to beremoved from the mold 28. In some embodiments, the mold 28 can include aplurality of mold cavities (e.g., 34) to increase overall productionrates.

The clamping unit 36 can apply a clamping force in the range ofapproximately 1000 P.S.I. to approximately 6000 P.S.I. during themolding process to hold the first and second mold portions 30, 32together in the clamped position. To support these clamping forces, themold 28, in some embodiments, can be formed from a material having asurface hardness from more than about 165 BHN to less than 260 BHN,although materials having surface hardness BHN values of greater than260 may be used as long as the material is easily machinable, asdiscussed further below. In some embodiments, the mold 28 can be a class101 or 102 injection mold (e.g., an “ultra-high productivity mold”).

The injection molding apparatus 10 can include a native controller 40that is in signal communication with various components of the injectionmolding apparatus 10. For example, the native controller 40 can be insignal communication with a screw control 44 via a signal line 45. Thenative controller 40 can command the screw control 44 to advance thereciprocating screw 18 at a rate that maintains a desired moldingprocess, such that variations in material viscosity, mold temperatures,melt temperatures, and other variations influencing filling rate, aretaken into account by the native controller 40. Adjustments may be madeby the native controller 40 immediately during the molding cycle, orcorrections can be made in subsequent cycles. Furthermore, severalsignals, from a number of cycles can be used as a basis for makingadjustments to the molding process by the native controller 40.

The native controller 40 can be any of a variety of suitable controllersfor controlling the molding process. In some embodiments, the nativecontroller 40 can be a PID controller. The native controller 40 can beresponsible for controlling a variety of different functions on theinjection molding apparatus 10, such as, for example, movement of theclamping unit 36 via a signal line 37. The native controller 40 can bean on-board controller that is original to the injection molding unit 12and built together with the injection molding unit 12. As such,modifications to the control architecture of the native controller 40can be time consuming, expensive and at times impossible.

In one embodiment, when the actuation unit 22 is a hydraulic motor, thescrew control 44 can comprise a hydraulic valve associated with thereciprocating screw 18. In another embodiment, when the actuation unit22 is an electric motor, the screw control 44 can comprise an electriccontroller associated with the reciprocating screw 18. In the embodimentof FIG. 1, the native controller 40 can generate a signal that istransmitted from an output of the native controller 40 to the screwcontrol 44.

Still referring to FIG. 1, a remote controller 46 can be in signalcommunication with the native controller 40, an injection pressuresensor 42 located in, at, or near, the actuation unit 22, and with acavity pressure sensor 50 located proximate an end of the mold cavity34. The injection pressure sensor 42 can facilitate detection (direct orindirect) of the injection pressure inside of the heated barrel 16(i.e., the pressure of the heated barrel 16 at the beginning of thereciprocating screw 18). The cavity pressure sensor 50 can facilitatedetection (direct or indirect) of the melt pressure of the moltenthermoplastic material 26 in, at, or near the nozzle 20. The cavitypressure sensor 50 may or may not be in direct contact with the moltenthermoplastic material 26. In some embodiments, the cavity pressuresensor 50 can be a pressure transducer that transmits an electricalsignal via a signal line 51 to an input of the native controller 40 inresponse to the cavity pressure within the mold cavity 34. In otherembodiments, the cavity pressure sensor 50 can facilitate monitoring ofany of a variety of additional or alternative characteristics of thethermoplastic material 26 or the mold 28 that might indicate cavitypressure, such as strain and/or flow rate of the molten thermoplasticmaterial 26, for example. If the cavity pressure sensor 50 is notlocated within the mold cavity 34, the native controller 40 can be set,configured, and/or programmed with logic, commands, and/or executableprogram instructions to provide appropriate correction factors toestimate or calculate values for the measured characteristic of the mold28.

As will be described in more detail below, the remote controller 46 cansense the injection pressure of the heated barrel 16 of the injectionmolding apparatus 10 and can send a signal (e.g., a modified feedbacksignal) to the native controller 40 that affects the manner in which thenative controller 40 controls the reciprocating screw 18. The remotecontroller 46 can be any of a variety of suitable controllers forproviding a modified feedback signal to the native controller 40 tofacilitate alternative control of the molding process. In someembodiments, the remote controller 46 can be a PID controller. In someembodiments, the remote controller 46 can be retrofitted onto theinjection molding unit 12 to provide additional functionality notcapable of being provided by the native controller 40.

Prior to retrofitting the remote controller 46 onto the injectionmolding apparatus 10, the native controller 40 can be in signalcommunication with the injection pressure sensor 42 (shown in dashedlines) located at the actuation unit 22. The injection pressure sensor42 can provide a feedback signal via a signal line 43 to the nativecontroller 40 that indicates the injection pressure inside of the heatedbarrel 16. The native controller 40 can detect the injection pressurefrom the feedback signal and can control (e.g., feedback control) theinjection pressure within the injection molding apparatus 10 bycontrolling the screw control 44, which controls the rates of injectionby the injection molding unit 12. To retrofit (e.g., associate) theremote controller 46 onto the injection molding apparatus 10, the outputfrom the injection pressure sensor 42 can be disconnected from thenative controller 40 and connected to the remote controller 46 therebydiverting the feedback signal from the injection pressure sensor 42 tothe remote controller 46. The cavity pressure sensor 50 can then becoupled to the remote controller 46 thereby completing the retrofit.Once the retrofit is complete, the native controller 40 no longerdirectly receives feedback signals from the injection pressure sensor 42or the cavity pressure sensor 50. Instead, the remote controller 46receives these feedback signals and transmits a modified feedback signalto the native controller 40 that enhances the operation of the nativecontroller 40, as described below. The native controller 40 and theremote controller 46 thus operate in a closed-loop type arrangement thatexisted prior to addition of the remote controller 46.

In some embodiments, the cavity pressure sensor 50 can already exist onthe injection molding unit 12 and can be in signal communication withthe native controller 40. In such an embodiment, the output from thecavity pressure sensor 50 can be disconnected from the native controller40 and reconnected to the remote controller 46. In some embodiments, thecavity pressure sensor 50 might not already exist on the injectionmolding unit 12. In such an embodiment, the cavity pressure sensor 50can be installed during retrofitting of the remote controller 46 andthen connected to the remote controller 46. For purposes of thisdisclosure, each of the melt pressure and the cavity pressure can beconsidered “controlled variables” whereas the injection pressure can beconsidered a “control variable.” A controlled variable can be understoodto be any characteristic of the thermoplastic material 26 or mold cavity34 that can be controlled to facilitate effective filling of the moldcavity 34. A control variable can be understood to be any characteristicof the injection molding unit 12 that can be controlled to facilitateeffective control of the reciprocating screw 18 or other injectionshaft.

An example block diagram of the feedback relationship between the nativecontroller 40 and the remote controller 46 is illustrated in FIG. 2 andwill now be discussed. At the remote controller 46, a setpoint P2 can beprovided via signal S3 that represents a desired injection pressure ofthe injection molding apparatus 10. A signal S5 can be provided to theremote controller 46 that indicates the measured injection pressure ofthe actuation unit 22. The actual injection pressure can be comparedagainst the setpoint P2 and an error signal E2 can be generated andprovided to a PID control algorithm G2 that generates a control signalC2. The control signal C2 and the signal S5 can be combined into amodified feedback signal S6. In some embodiments, the modified feedbacksignal S6 can also include a feedforward component FF1. The modifiedfeedback signal S6 can additionally or alternatively include any of avariety of other suitable control components that facilitate generationof an effective modified feedback signal.

The modified feedback signal S6 can be transmitted to the nativecontroller 40 in lieu of the feedback signal from the injection pressuresensor 42 (shown in dashed lines on FIG. 1). In one embodiment, themodified feedback signal S6 can be transmitted over a unidirectionaltransmission link between the native controller 40 and the remotecontroller 46. In such an embodiment, the native controller 40 does nottransmit any signals to the remote controller 46.

At the native controller 40, the operation of the actuation unit 22 canbe controlled according to the modified feedback signal S6. For example,a setpoint P1 can be provided via signal S1 that represents a desiredinjection pressure of the actuation unit 22. The setpoint P1 can becompared against the modified feedback signal S6 and an error signal E1can be generated. The error signal E1 can be provided to a PID controlalgorithm G1 that generates a control signal C1 that commands the screwcontrol 44 to advance the reciprocating screw 18 at a rate that causesthe injection pressure to converge towards the desired injectionpressure indicated by the setpoint P1.

Although the native controller 40 is controlling to the desiredinjection pressure of the setpoint P1, the modified feedback signal S6from the remote controller 46 can affect the control signal C from thenative controller 40 in a manner that actually controls the injectionpressure of the injection molding apparatus 10 to the desired pressuredefined by the setpoint P2 (rather than controlling the injectionpressure of the actuation unit 22 to the setpoint P1). The remotecontroller 46 can thus provide the capability to control the injectionpressure of the injection molding unit 12 without requiringreprograming/reconfiguration of the control architecture of the nativecontroller 40. As such, the remote controller 46 can be a cost effectiveand straightforward solution to add functionality to the injectionmolding apparatus 10 where the native controller 40 is not capable ofproviding such functionality independently.

During a molding cycle, the injection pressure of the injection moldingunit 12 can be changed by changing the setpoint P2. In one embodiment,different setpoints can correspond to a different stage of the moldingcycle. For example, to initiate the initial injecting stage, a setpointcan be provided that causes the melt pressure to increase enough tobegin melting the thermoplastic pellets 24 and distributing the melt tothe nozzle 20. Once the melt pressure has increased enough to beginfilling the mold cavity 34, a setpoint can be provided that initiatesthe filling stage at a pressure that is appropriate to properly fill themold cavity 34. Once the mold cavity 34 is almost filled (e.g., end offill), a setpoint can be provided to decrease enough to initiate thepacking stage and hold at a substantially constant melt pressure duringthe holding stage.

The native controller 40 and/or the remote controller 46 can beimplemented in hardware, software or any combination of both and canhave any control arrangement having one or more controllers foraccomplishing control. It is to be appreciated that, although the nativecontroller 40 is described as sensing and controlling the injectionpressure of the actuation unit 22, a native controller 40 can beconfigured to sense and control any of a variety of suitable alternativecontrol variables, such as, for example, a temperature of the heatedbarrel 16, a volume of the hopper 14, or velocity of the reciprocatingscrew 18. It is also to be appreciated that, although the remotecontroller 46 is described as providing the capability to control theinjection pressure of the injection molding unit 12, a remote controllerusing the injection pressure of the actuation unit 22 can be configuredto sense and control any of a variety of suitable alternative controlvariables, such as, for example, cavity pressure.

The foregoing description of embodiments and examples has been presentedfor purposes of illustration and description. It is not intended to beexhaustive or limiting to the forms described. For, example, althoughthe remote controller 46 is described as being provided on an injectionmolding apparatus, a remote controller can be provided on any apparatusthat employs feedback control from a native controller to addfunctionality to the apparatus where the native controller is notcapable of providing such functionality independently. Numerousmodifications are possible in light of the above teachings. Some ofthose modifications have been discussed and others will be understood bythose skilled in the art. The embodiments were chosen and described forillustration of various embodiments. The scope is, of course, notlimited to the examples or embodiments set forth herein, but can beemployed in any number of applications and equivalent devices by thoseof ordinary skill in the art. Rather it is hereby intended the scope bedefined by the claims appended hereto. Also, for any methods claimedand/or described, regardless of whether the method is described inconjunction with a flow diagram, it should be understood that unlessotherwise specified or required by context, any explicit or implicitordering of steps performed in the execution of a method does not implythat those steps must be performed in the order presented and may beperformed in a different order or in parallel.

The dimensions and values disclosed herein are not to be understood asbeing strictly limited to the exact numerical values recited. Instead,unless otherwise specified, each such dimension is intended to mean boththe recited value and a functionally equivalent range surrounding thatvalue. For example, a dimension disclosed as “40 mm” is intended to mean“about 40 mm.”

Every document cited herein, including any cross referenced or relatedpatent or application and any patent application or patent to which thisapplication claims priority or benefit thereof, is hereby incorporatedherein by reference in its entirety unless expressly excluded orotherwise limited. The citation of any document is not an admission thatit is prior art with respect to any invention disclosed or claimedherein or that it alone, or in any combination with any other referenceor references, teaches, suggests or discloses any such invention.Further, to the extent that any meaning or definition of a term in thisdocument conflicts with any meaning or definition of the same term in adocument incorporated by reference, the meaning or definition assignedto that term in this document shall govern.

While particular embodiments of the present invention have beenillustrated and described, it would be obvious to those skilled in theart that various other changes and modifications can be made withoutdeparting from the spirit and scope of the invention. It is thereforeintended to cover in the appended claims all such changes andmodifications that are within the scope of this invention.

What is claimed is:
 1. An injection molding apparatus comprising: aheated barrel; an injection shaft disposed in the heated barrel andconfigured to rotate with respect to the heated barrel; an actuationunit operably coupled with the injection shaft and configured tofacilitate an operation of the injection shaft with respect to theheated barrel; a clamping unit for a mold, the clamping unit beingassociated with the heated barrel; a nozzle disposed at one end of theheated barrel and configured to distribute contents of the heated barrelto the clamping unit; a native controller in communication with theactuation unit and configured to facilitate the operation of theinjection shaft; a remote controller in communication with the nativecontroller; a sensor in communication with the remote controller andconfigured to sense a control variable of the injection shaft andgenerate a feedback signal based upon the control variable; wherein theremote controller is configured to: receive the feedback signal from thesensor; define a desired setpoint for the control variable; compare avalue of the control variable to the desired setpoint of the controlvariable; generate a control signal based upon the comparing of thecontrol variable and the desired setpoint of the control variable;combine the control signal and the feedback signal into a modifiedfeedback signal; and transmit the modified feedback signal to the nativecontroller in lieu of the feedback signal; and wherein the nativecontroller is configured to control the operation of the actuation unitbased at least in part upon the modified feedback signal.
 2. Theinjection molding apparatus of claim 1, wherein: the sensor is aninjection pressure sensor that is configured to sense an injectionpressure of the heated barrel and generate an injection pressure signal;and the remote controller is further configured to receive the injectionpressure signal from the injection pressure sensor and determine a valuefor the injection pressure based upon the injection pressure signal. 3.The injection molding apparatus of claim 1, wherein the remotecontroller is a retrofit-type controller.
 4. The injection moldingapparatus of claim 1, wherein the modified feedback signal istransmitted over a unidirectional transmission link between the nativecontroller and the remote controller, and the native controller does nottransmit any signals to the remote controller.
 5. The injection moldingapparatus of claim 1, wherein the injector shaft includes areciprocating screw.